The present invention relates to a copying maching having a plurality of photosensitive members and an image transfer belt movable in synchronism with rotations of the photosensitive members for transferring visible images formed on the photosensitive members onto a transfer paper carried by the transfer belt and, particularly to a method for controlling an operation of the copying machine.
In a conventional copying machine of such type as mentioned above, a copy is obtained through a copying process including the steps of electrostatically charging the photosensitive members, esposing the photosensitive members with an original image to form latent images thereon, developing them, transferring the developed images onto the copy paper and cleaning them for subsequent use. Prior to this process, the photosensitive members may be preprocessed to remove electric charges thereon and clean them up.
The process including the preprocess, if any, is generally sequence-controlled by using encoder pulses generated in synchronism with revolutions of the photosensitive members. That is, the process is controlled according to revolutions of the photosensitive members. When a movement of the transfer belt is in synchronism with the photosensitive members, it can be said that the process is controlled by the transfer belt. However, such synchronism is obtained after a certain portion of the transfer belt is positioned at a predetermined location on a path thereof, a relative position of the transfer belt with respect to the copying process depends upon a setting of the transfer belt in the copying machine. In a case where the transfer belt has a seam, a relative position of the seam with respect to the process becomes fixed after the transfer belt is incorporated in the copying machine. However, an absolute position of the seam may vary with respect to the process.
When the transfer belt is set in the copying machine such that the seam thereof comes into an image transfer position on the belt during a visible image transfer from one of the photosensitive members to the transfer paper carried on the belt, there may be an incomplete contact of the transfer paper with the photosensitive members due to a presence of the seam, resulting in a partially blurred image on the transfer paper.